Fix reason firmly in her seat, and call to her tribunal every fact, every opinion. Question with boldness even the existence of a God; because, if there be one, he must more approve the homage of reason than of blindfolded fear. Do not be frightened from this inquiry by any fear of its consequences. If it ends in a belief that there is no God, you will find incitements to virtue in the comfort and pleasantness you feel in its exercise and in the love of others which it will procure for you. (Thomas Jefferson)

Religion is a byproduct of fear. For much of human history, it may have been a necessary evil, but why was it more evil than necessary? Isn't killing people in the name of God a pretty good definition of insanity? (Sir Arthur C. Clarke)

Imagine encouraging a child to participate in such 'twisted' rituals and worshiping of tortuous crucifixes and such like this from birth. No wonder we have so many hateful and sadistic people in our society. (Brent Allsop)

On the other hand, famous evolutionists such as Dobzhansky were firm believers in a personal god. He would work as a scientist all week and then on Sunday get down on his knees and pray to God. Frankly I’ve never been able to understand it because you would need two totally different compartments in your brain, one that deals with religion and the other with everything else. (Ernst Mayr)

I am a hopeless materialist. I see this all as nothing else than the sum of activities of the organism plus personal habits, inherited habits, memories, experiences, of the organism. I believe that when I am dead, I am dead. I believe that with my death I am just as much obliterated as the last mosquito you squashed. (Jack London)

Never yet has a god been defined in terms which were not palpably self-contradictory and absurd; never yet has a god been described so that a concept of Him was made possible to human thought. (Annie Besant)

Religious controversies are always productive of more acrimony and irreconcilable hatreds than those which spring from any other cause. I had hoped that liberal and enlightened thought would have reconciled the Christians so that their (not our) religious fights would not endanger the peace of Society. (George Washington)

It is because one can build a compelling set of arguments, informed by science and thoroughly compatible with it, that to believe in anything despite the complete lack of evidence is, in fact, irrational. (Dr. Massimo Pigliucci)

Religion has actually convinced people that there's an invisible man, living in the sky, who watches everything you do, every minute of every day. And the invisible man has a special list of ten things he does not want you to do. And if you do any of these ten things, he has a special place, full of fire and smoke and burning and torture and anguish, where he will send you to live and suffer and burn and choke and scream and cry forever and ever 'til the end of time! But He loves you. (George Carlin)

What havoc has been made of books through every century of the Christian era? Where are fifty gospels, condemned as spurious by the bull of Pope Gelasius? Where are the forty wagon-loads of Hebrew manuscripts burned in France, by order of another pope, because suspected of heresy? Remember the 'index expurgatorius', the inquisition, the stake, the axe, the halter and the guillotine. (John Adams)